<!DOCTYPE html>
<html style="reftest-wait">
<head>
    <style>
        #target {
            width: 100px;
            height: 100px;
            background: green;
            margin: 300px;
        }
    </style>
</head>
<body>
    <div id="target"></div>
    <div style="height: 1000px"></div>
    <script>
        function scrollBy(y) {
            return new Promise(resolve => {
                addEventListener("scroll", () => {
                    requestAnimationFrame(() => {
                        requestAnimationFrame(resolve);
                    });
                }, { once: true, capture: true });
                document.documentElement.scrollBy({
                    top: y,
                    behavior: "instant"
                });
            });
        }
        addEventListener("load", async () => {
            await scrollBy(200);
            document.documentElement.classList.remove("reftest-wait");
        });
    </script>
</body>
</html>
